This invention relates to a reflector made from a fiber reinforced plastic, and more particularly it relates to a reflector which is capable of reflecting light rays ranging in frequency from the infrared to the ultraviolet region.
FIGS. 1 and 2 are cross-sectional view of two conventional reflectors made from a fiber reinforced plastic (hereinunder abbreviated as FRP). Each of the reflectors has a core 1 which is made from a honeycomb material or a polymer foam. An FRP plate 2 is bonded by a bonding agent 3 to each side of the core 1. One example of a material for the FRP plates 2 is a carbon fiber reinforced plastic (abbreviated as CFRP). A reflecting film 4 which can reflect light rays ranging in frequency from the infrared to the ultraviolet region is formed on the other surface of one of the FRP plates 2 by vapor deposition or other suitable method. The reflector is rigidly supported by a base 5 through a support member 6 which is secured to both the base 5 and one of the FRP plates 2. The reflector of FIG. 2 further comprises a hard and smooth substrate 7 of glass, metal, or the like which is formed on one of the FRP plates 2 beneath the reflecting film 4.
When the core 1 of a conventional reflector like those illustrated in FIGS. 1 and 2 is a honeycomb core, due to the anisotropy of the honeycomb core with respect to mechanical and thermal properties, nonuniform deformation may take place in the form of saddle-shaped molding strains and thermal deformation. Even if the honeycomb core is divided into a plurality of members which are disposed with consideration given to the directionality of the properties of the honeycomb material, each of the members making up the honeycomb core is still anisotropic, and nonuniform molding strains and thermal deformation can not be completely eliminated. Furthermore, when the honeycomb core is divided up in this manner, the reflecting surface undergoes deformation due to lack of structural continuity. As a result, when the reflector is used to reflect light rays and form an image, a sharp image can not be obtained. Furthermore, when the reflector is used to reflect light rays which are emitted from the focus of the reflector, the reflector can not produce parallel light rays having a uniform intensity distribution.
On the other hand, when the core 1 is made of a polymer foam, since the foam is a uniform material, there are no nonuniform deformations. However, a polymer foam has a relatively high linear thermal expansion coefficient on the order of 3-7.times.10.sup.-5 /.degree.C., and the thermal deformation of the reflector is large compared to that of one having a honeycomb core made of aluminum, for example. Furthermore, a reflector of this type having a sandwich construction with a polymer foam as a core is disadvantageous in that it has a lower stiffness-to-weight ratio than one employing a honeycomb core.